The Transgenic and Chimeric Mouse Core supports the overall mission of the Penn DRC to prevent, treat, and cure diabetes mellitus. The accelerating incidence of diabetes and metabolic disorders and the continuing high prevalence of endocrine disorders in the American population demands continued exploration of a broad array of corresponding mechanistic pathways, pathophysiologic sequelae, and potential therapeutic approaches. In many cases these investigations can be accomplished most efficiently using model systems established in intact animals. The use of mouse models in these pursuits is now well established for its power, feasibility, and enormous potential. The development of such models, by directed alterations of the mouse genome, while of high utility, remains a technically demanding and labor intensive component of an overall research effort in diabetes, obesity, and metabolic disorders. The Transgenic and Chimeric Mouse Core provides investigators of the Penn Diabetes Research Center (DRC) with the ability to carry out these studies in a cost effective and efficient manner. The TCMF applies state-of-the-art equipment and technology by a group of dedicated and highly skilled technical staff to this effort. The major services of the Core include generation of transgenic mice by pronuclear injection, creation of chimeric mice by blastocyst injections, assisted fertilization, cryopreservation, long-term cryostorage, and shipping of frozen embryos or sperm to other facilities. The Core uses multiple microinjection platforms, laser-assisted technologies, state-of-the-art cryopreservation of gametes and embryos, and in vitro fertilization based line re-derivation to facilitate these goals. The facility consists of a microinjection suite, an adjacent dedicated cage room and an off-site cryopreservation storage facility. All functions, from ordering services, to following work flow, to storing and sending out lines is now on-line and can be monitored in real-time. These efforts contribute substantially to the overall productivity of the members of the DRC and enhance the strength and relevance of their studies to intact mammalian systems. This maximizes the applicability of these studies to human disease and its therapeutics.